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Old 03-01-2013, 02:30 PM   #1
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Post Excellent 2014 Corvette Stingray In-Depth Interview w/ the People Who Made It Happen

From the March 2013 Issue of Car and Driver

We are now intimate with the 2014 Corvette Stingray. Yep, Stingray. The historic moniker is not being reserved, as we previously proposed, for a later de-powered model, but goes on the base car. And now we know far more than its name. We’ve gazed upon its inner organs, examined its bones, and touched its skin. It all looks extremely promising, and makes the dramatic departure from the C6 that we projected in our January cover story.

Prior to its reveal earlier this year at Detroit’s North American International Auto Show, Chevrolet raised the veil slightly higher, providing limited access to a full-scale exterior model, a mock-up of the interior, the aluminum space frame, and many other components. More important, Car and Driver was granted eight hours with the engineers, designers, and specialists who were finally free to speak on the record about what they’ve been doing for the past three and a half years. When PR pulled the secrecy cork, the experts *bubbled over with enthusiasm and details.





GM made most C7 styling decisions in the wind tunnel (Stingray badge excepted); taillamps eschew pre-Transformers tradition. Top right: Kirk Bennion, Design Manager.


The new Stingray puts chief engineer Tadge Juechter’s stamp on Corvette legacy as firmly as the 1984 C4 did Dave McLellan’s and the ’97 C5 did Dave Hill’s. There will be base (Stingray) and Z51 models at launch this fall, and Juechter has packed the car with high-end drivetrain, aerodynamic, and material technologies, giving every C7 an aluminum structure, carbon-fiber hood and roof panels, a composite sandwich floor, and the new 450-hp small-block V-8. Juechter’s been working on Corvette for nearly 20 years, starting as the total vehicle integration engineer on the C5. He was assistant chief on the C6 and got the top job in mid-2006. The C6 was meant to have a shorter run, with C7 development commencing in 2007, but the project stalled, so Juechter stayed busy freshening the C6 with programs including the ZR1 and 427 convertible. Here’s what he and other key members of the C7 team had to say about the new car:
What was it like while the C7 was in a holding pattern?
Juechter:

We’d get started, then stopped. Started again, then stopped. As GM moved toward bankruptcy, we kept getting stopped, postponed, and then after bankruptcy we felt like we were on good footing. The Treasury Department looked at the total portfolio of vehicles and quite honestly there were some Corvette fans amongst the consultants and at Treasury. When they saw that it made money . . . they saw that it would be good for everybody to get rolling on the Corvette.
Is this car a more dramatic departure than envisioned pre-bankruptcy, because it's coming later?
Juechter:

We wanted a big upgrade, more like the change from C4 to C5 than the evolution from C5 to C6. That was always in the plan. As we got into it, it turned out to be even bigger than we thought. We thought we could take today’s aluminum frame and tweak it. It turns out we had to scrap the whole thing and start over, the technologies had moved on so far. Everything’s so highly integrated that once you take one thing it telegraphs into *others and you can’t just mandate your way in. You’ve gotta say, “Y’know what? We need a blank sheet of paper.”





Right: Ryan Vaughn, Interior Design Manager.



What should people notice looking at the car?

Kirk Bennion, Design Manager:

It starts at the front, because it’s not a bottom-breather [with a horizontal cooling air intake under the nose] anymore. We found that bottom-breathers don’t really work all that well when you start to see the speeds that our cars are seeing on tracks. Before we even started the rest of the program, we were having offline meetings about changing the CRFM [condenser/radiator/fan module] position. Instead of leaning the radiator back, we leaned it forward, taking a cue from our race team. Leaning it forward allows us to force-feed the air in, and then dump it out over the top of the hood. This enables the front-end architecture to have more downforce inherently. Now, half the air goes over the top and less than half is spilling out through the sides. That is a big win for us in moving this car to the next level.

John Bednarchik, Aerodynamics Performance Engineer:

Also coming from the way the race team does it, we have coolers for the transmission and differential mounted at the rear. Each is located in a lower outboard corner, with exits in the rear fascia. The air goes in through the inlet that you can see on the top of the quarter-panel and is ducted directly to a cooler. On the driver’s side is the trans oil cooler; the passenger side is the differential cooler.

Bennion:

They’re not just aesthetic things that we bolt on. The hood air extractor’s vanes are shaped and angled to manage airflow, and they tip down as they go back. Another example: Starting with the ’56 model, the Corvette always had side coves, and we can’t imagine not having those. But even there, we’ve made them functional. John and I have measured air coming through there, and it is relieving underhood pressure and lowering the Cd of the car.


How did traditionalists respond to those new taillights when you showed the car in clinics?


Juechter:

We never clinic’d the exterior. We did clinic the interior, stripped of identification, against a [Porsche] 911, an [Audi] R8, and Nissan GT-R, but we knew people would recognize the exterior for what it was and talk about it, and we didn’t want that.

Bennion:

We wanted to do dual taillamps, which has been a Corvette signature, but something that was unique, that would say “This is a new Corvette.” Not only does it have to say Corvette, but we felt it had to say new Corvette. It’s in the Chevy family, but more dimensional and sculpted. From what feedback we have, the younger group likes these.





The C7 offers a smaller steering wheel, adaptive dash, and seven speeds. Better seats, too. Can we get a hallelujah?


Why does the interior depart from the dual-cockpit heritage cues?

Ryan Vaughn, Interior Design Manager:

We knew we didn’t want to go down the retro path of symmetrical dual cockpits, like a literal interpretation of a ’63. We started with this idea of a driver-oriented environment and built up from there. By giving the passenger their own dedicated climate and seat heating/cooling controls, the passenger doesn’t need to reach into the driver’s area. The electronic parking brake is a huge packaging enabler. Without the mechanical brake *handle, there’s room for a more ergonomic console, cup holder, and storage, and it leaves enough room for the shifter and to move your arm in that whole area.
Juechter:

The interior is probably the single most upgraded area of the car. It’s a fully wrapped interior; you won’t see any molded-color plastic anywhere. Even the base car is fully wrapped. Even without the leather option or the carbon-fiber trim option, you get high-quality vinyl, cut and sewn, and premium painted surfaces and aluminum trim, with upgraded soft-touch materials. We sent our interior-design folks to the track. We wanted them to understand that the cockpit isn’t just a comfortable and attractive setting but a high-tech working environment on the track. Everything has to function at speed.

We've long complained about Corvette's seats. Please, please tell us you've fixed them.

Juechter:

Many of our customers are happy with today’s seats, but there’s a core out there that drives their cars aggressively, including visits to the track, and they’ve been unsatisfied with the level of lateral support. So we put a lot of science into our seats. For the first time, we elected to spend the money and engineering resources on two distinct seats. One, the GT seat or touring-type seat, has improved lateral support over today’s seat but is engineered for long-range comfort. Then there’s a true competition seat. We use a magnesium support frame shaped for lateral support that is firmer than the composite frame we have today. And we’ve got seatbelt cutouts in both seats, so you can put through four-inch-wide, five-point harnesses. We benchmarked Porsche seats that also are produced by Lear, our supplier, and Recaro seats purchased for other GM programs, and we did some scientific evaluation. We scanned those seats and measured the pressure and support on the track. We think you’ll be pleased with both. We’ll advise customers to try the competition seat before ordering it; it’s not going to be comfortable for larger people.






HEAVY HARDWARE: Direct injection, variable valve timing, and cylinder deactivation improve small-block efficiency, though the componentry adds both mass and length.



There's rev-matching on both up- and downshifts in the seven-speed manual transmission?

Juechter:

We looked at what others had done, and we’ve added rev-matching on upshifts. We invented and patented this sensor that, when you move the shifter, actually anticipates what you’re going to do. You can move the shifter toward a gate and see on the tach the revs that the system is going to give you, and you can hear it. You can almost play it like a musical instrument. It can also be shut off because sometimes you find that you just want it to act like a traditional shifter. To do that, we use paddles behind the steering wheel like you’d find for shifting an automatic. We also have AFM [active fuel management, or cylinder deactivation] even with the manual, which no one else is doing.
Did you consider a dual-clutch automatic?
Juechter:

Nothing available will fit and can handle our torque [estimated at 450 pound-feet]. The same thing with an eight-speed automatic. So we’re staying with a six-speed auto with a torque converter. You can be far more aggressive on cylinder deactivation when you’ve got a torque converter in the car. The number of speeds isn’t everything. We introduced C6 with a four-speed automatic and brought in a six-speed in the second year, and had a hell of a time beating the four-speed on both fuel economy and performance. We operate at high torque, high efficiency across a broad rpm range, so we don’t need more gears. That said, we see the market going to more speeds, so we’ll keep an eye on that and when we can offer genuine improvement in fuel economy with more speeds, we will.


Did you consider other engines?

Juechter:

Early on we examined all the alternatives. We looked at a V-6 and V-6 turbo, as well as a smaller V-8. The result wasn’t what you’d expect; it wasn’t better performance and better fuel economy. The Gen V 6.2-liter with direct injection, cylinder deactivation [AFM], and variable valve timing gives us both the performance and fuel-economy gains. A big factor is AFM. If we went to the smaller 5.0 V-8 we looked at, we don’t get enough torque in the 2.5-liter four-cylinder mode to stay in that mode very long. It’s kind of counterintuitive, but the 6.2, running as a 3.1-liter four can be in that mode a lot more often and for longer, so it returns better fuel economy. Similarly, competitors run smaller engines and rev them harder to get the performance. When you spin ’em that fast, consumption goes up a lot.
You benchmarked the Porsche 911, the Audi R8, and the Nissan GT-R. Is fuel economy a sales concern in this segment?
Juechter:

When I go to Corvette events, the first thing people tell me is not how fast they got there, but what fuel economy they got on the way. The owners care. If you do a survey, it’s not in their top reasons for *purchase, maybe not even the top five, but there won’t be a Corvette if we don’t care about fuel economy.





Right: Here’s the standard seat from Lear, also a supplier to Porsche. Unlike the sport seat (bottom, left), it’s roomy enough for fat guys.



Why do you need a dry-sump in the Z51 Performance package?

Juechter:

We’ve got a lot of testing under our belt and we know we’re going to be under 4.0 seconds, 0 to 60. We’ve got improved braking distances, with the base car approaching today’s Z06, and more than 1.0 g in cornering. There’s a lot of g-loading, so a top-flight lubrication system is required.

John Rydzewski, Assistant Chief Engineer, Small-Block Engines:

We built a tilt-rig up in Pontiac that’s kind of wild to watch. It creates the same g-loadings you get on a track by tilting the engine side to side and forward and back, all while it’s turning at 6600 rpm. We use a variable-displacement oil pump because a lot of the engine’s technology [AFM, variable valve timing, etc.] runs on hydraulics. There’s more oil flow through the engine and we want to minimize variation in the pressure. The usual pump might flow too much at high speed, too little, maybe, at low revs with a high cornering load. The new engine has a vane pump, not new technology, but it maintains the same pressure whether the oil is cold and thick or hot and less viscous. There’s feedback from the main bearing cap, so it knows exactly what the number-one main bearing is reading and adjusts to maintain that pressure.





Ducts for rear-mounted cooling influenced roof and window shapes; the car wears Dunlop tires for photos, Michelins in real life. Top right: Mike Bailey, Vehicle Systems Engineer, Chassis. Bottom left: Ed Moss, Engineering Group Manager, Structure.


Instead of the previous one-piece, full-length hydroformed frame rails, you've now got a complex assembly of tubes, castings, and extrusions. Why?

Ed Moss, Engineering Group Manager, Structure:

There are five major aluminum parts per side. That allowed us to optimize gauges from 2 millimeters [0.08 inch] to 11 millimeters [0.43 inch]. On the C6 Z06, it’s 4 millimeters [0.16 inch] end to end. This [assembly] lets us optimize stiffness not only overall, but locally. So you’ve got an extruded crash structure at the front. Then a casting where the cradle mounts. Then tubing by the cockpit. Then a casting for the rear-suspension cradle, and then the rear crush part.

What else is new down there?

Mike Bailey, Vehicle Systems Engineer, Chassis:

Our lower control arms, which are hollow, are cast aluminum, saving about 4 kilograms [9 pounds] of mass. And they’ve gone up in stiffness considerably because we’ve moved the mass outboard, increasing the moment of inertia. With stiffer parts, we can tune in with our bushings better, and, because half of the control arms are unsprung mass, *savings here are extra effective.
Moss:

The center tunnel is also completely redesigned, and that part’s actually heavier than in today’s aluminum car because we needed the strength for the open-roof car. The overall mass of the metal parts alone is down 99 pounds, from the steel-framed open car to the new aluminum version. Even if you latch a roof into the C7 and compare it to today’s Z06 with the solid roof, it’s more than 50 percent stiffer.

Juechter:

And we’ve finally found something better than balsa wood! It’s still a sandwich floor, but it’s a composite material that is stronger and lighter than the wood.


How did you manage to keep the 50/50 weight balance?

Bennion:

The new engine is a little longer, with the variable-valve-timing hardware at the front, which is why the wheelbase is an inch longer. These cars have always been considered by chassis guys to be front/mid-engine cars and now the engine is fully behind the front axle. Moving the coolers and the battery to the back helps.

Juechter:

We’re actually better than 50/50, we’re a little rear-biased, getting closer to the race car’s 48/52 front-rear balance.

What's new with the brakes?

Bailey:

We’ve got two distinct brake systems for two distinct cars. The base C7 has 35 percent more swept area than the base C6. The C7 Z51 has 6 percent more swept area than the current Z06. They’re some pretty awesome brakes. The guys who’ve run mules at VIR are getting lap times competitive with today’s Z06. This is a dual-cast rotor. It’s got an inner [aluminum] web and an outer [cast-iron] rotor and the beauty of this is you can allow for the thermal expansion of the rotor without affecting the hub geometry, so you can make them out of two different materials. We’ve gone away from holes that go through the rotor, because there have been instances of breakage there. New surface slots give you some initial bite that the development engineers say they feel, plus, at speed, they evacuate gasses off the pad.





THEM’S THE BRAKES: Larger rotors and fixed calipers promise eye-bleeding stops; Z51’s dual-cast rotor (shown). Other Z51 markers: rear spoiler and 19-inch front, 20-inch rear wheels, bigger MSRP (not shown).


What's with your devotion to the transverse leaf springs?

Bailey:

We try not to say leaf. It makes people think of pickup trucks, and it’s not like that at all. It’s an engineered composite spring. It’s got a low CG [center of gravity], it’s light, it provides some anti-roll contribution, and it packages well, enabling a low hoodline. We know there are a lot of aftermarket suppliers for coil-overs for our car, but there’s a difference between that and an actual, true production car when it runs through a validation process.

The magnetorheological shocks are still an option?

Bailey:

There are three shocks: Standard is this 35-mm [1.4-inch] Bilstein monotube. The Z51 uses a 45-mm [1.8-inch] Bilstein, and Magnetic Ride Control is optional on Z51.

Electric-assist power steering? Really?

Juechter:

Yes, electric assist. We reengineered every single part from the wheel where your fingers touch through the tilt mechanism, through the steering shaft, through the solid-mounted steering rack, and after we reengineered that stuff we measured the system and it’s five times stiffer than today’s. Five times! I didn’t believe it; I asked for proof. You get exactly proportional response when you turn the wheel. We’ve got a smaller-diameter 360-mm [14.2-inch] steering wheel. We started C5 at 386 [15.2 inches], then we did a 380 [15.0 inches] and a 376 [14.8 inches], and now we’re down to 360, very close to a true racing size. The trick with the small wheel is getting a good view of the cluster, and everyone expects buttons and control modes located there. And you’ve gotta shrink the airbag and meet driver safety requirements, so there are two big engineering challenges.





ALLOY THERE: Stiffer than today’s steel hydroformed rails, C7’s frame joins aluminum extrusions (A) engineered to absorb crash energy; castings (B) for firm, precise suspension and steering mounts; and hydroformed tubes (C) for weight savings.


Variable effort for the steering is something the driver selects?

Juechter:

It’s one of up to 12 variables, so we decided to integrate these controls with the Driver Mode Selector on the console. You choose the mode: weather for snow or rain, eco that will maximize use of AFM, sport for fast road driving, and a setup for track use.

So why is it a Stingray?

Juechter:

We didn’t know for sure if we were going to rechristen the car the Stingray. [Vice president of global design] Ed Welburn was extremely strong on this point. He said, “I’m not going to sign off to call it a Stingray until we see how it turns out.” He meant that Stingray is a hallowed name in automotive history, representing a combination of striking styling along with a certain type of design language that kind of evokes a stingray, along with commensurate technology. One of the last decisions we made on the car was whether or not to call it a Stingray, and when we’re all said and done, we went through the technology, the design, and the new interior, and there was no question.
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Old 03-01-2013, 04:12 PM   #2
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Good read. One sentence sums it up for me... I want to get intimate with the new Stingray. :madgrin:
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Old 03-03-2013, 08:50 AM   #3
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Great interview, the C7 should be VERY interesting when it arrives

Long time Corvette fan.
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Old 03-03-2013, 01:30 PM   #4
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Great info and insight! Thanks!

Still waiting to see it in person. And I'm still steaming that GM didn't show the C7 at St Louis...... That's where the "original" Stingray was built..... What better way to tie it all together....
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Old 03-03-2013, 01:35 PM   #5
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It's only going to major auto shows for now. There aren't enough show-worthy C7s to go around.
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Old 03-03-2013, 02:50 PM   #6
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And a few major concours d'elegance shows... it's supposed to make an appearance at the Amelia show on the 8th... Ed Welburn too.
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Old 03-03-2013, 03:01 PM   #7
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Yep. Completely understand the reason why it didn't show up in St Louis.....but "selfishly" I don't have to like it!
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Old 03-03-2013, 05:29 PM   #8
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Great Thread!!!


I have been fortunate
...to have seen it...



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Old 03-03-2013, 06:18 PM   #9
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Quote:
Originally Posted by BeckyD@RodgersChevrolet View Post
Great Thread!!!


I have been fortunate
...to have seen it...


Ditto!
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